One of the simplest and most effective ways to teach puppies not to bite is to simply stop all play and attention as soon as they nip. Since most puppy biting is playful, this teaches them that biting results in the opposite of what they want.
Biting is a normal part of play for dogs, and puppies have to learn when it is appropriate and how hard they can bite. This begins when they are still with their mother and litter mates. The mother usually gets up and leaves if her puppies bite while nursing or playing. Puppies should be left with their mother for eight to 10 weeks to help this social development.
Puppies can also be taught what to do instead of biting. This can be done with a clicker or marker word. An easy exercise is to hold your closed fist out to the puppy and reward the puppy for gently touching or licking it. Once the puppy is reliably touching your hand while it is still, start moving it around and continue to reward the puppy for gentle touches. If the puppy nips, hold still but do not otherwise react. Puppies can also be taught to close their mouths on command to prevent nipping. Some people say "ouch" or make a yelping sound when the puppy nips as well.